Coro/Coro.pm

=head1 NAME

Coro - coroutine process abstraction

=head1 SYNOPSIS

 use Coro;

 async {
    # some asynchronous thread of execution
 };

 # alternatively create an async process like this:

 sub some_func : Coro {
    # some more async code
 }

 cede;

=head1 DESCRIPTION

This module collection manages coroutines. Coroutines are similar to
Threads but don't run in parallel.

This module is still experimental, see the BUGS section below.

In this module, coroutines are defined as "callchain + lexical variables
+ @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own
callchain, it's own set of lexicals and it's own set of perl's most
important global variables.

=cut

package Coro;

use Coro::State;

use base Exporter;

$VERSION = 0.45;

@EXPORT = qw(async cede schedule terminate current);
%EXPORT_TAGS = (
      prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
);
@EXPORT_OK = @{$EXPORT_TAGS{prio}};

{
   my @async;
   my $init;

   # this way of handling attributes simply is NOT scalable ;()
   sub import {
      Coro->export_to_level(1, @_);
      my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
      *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
         my ($package, $ref) = (shift, shift);
         my @attrs;
         for (@_) {
            if ($_ eq "Coro") {
               push @async, $ref;
               unless ($init++) {
                  eval q{
                     sub INIT {
                        &async(pop @async) while @async;
                     }
                  };
               }
            } else {
               push @attrs, $_;
            }
         }
         return $old ? $old->($package, $ref, @attrs) : @attrs;
      };
   }

}

=item $main

This coroutine represents the main program.

=cut

our $main = new Coro;

=item $current (or as function: current)

The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course).

=cut

# maybe some other module used Coro::Specific before...
if ($current) {
   $main->{specific} = $current->{specific};
}

our $current = $main;

sub current() { $current }

=item $idle

The coroutine to switch to when no other coroutine is running. The default
implementation prints "FATAL: deadlock detected" and exits.

=cut

# should be done using priorities :(
our $idle = new Coro sub {
   print STDERR "FATAL: deadlock detected\n";
   exit(51);
};

# this coroutine is necessary because a coroutine
# cannot destroy itself.
my @destroy;
my $manager = new Coro sub {
   while() {
      delete ((pop @destroy)->{_coro_state}) while @destroy;
      &schedule;
   }
};

# static methods. not really.

=head2 STATIC METHODS

Static methods are actually functions that operate on the current process only.

=over 4

=item async { ... } [@args...]

Create a new asynchronous process and return it's process object
(usually unused). When the sub returns the new process is automatically
terminated.

   # create a new coroutine that just prints its arguments
   async {
      print "@_\n";
   } 1,2,3,4;

The coderef you submit MUST NOT be a closure that refers to variables
in an outer scope. This does NOT work. Pass arguments into it instead.

=cut

sub async(&@) {
   my $pid = new Coro @_;
   $manager->ready; # this ensures that the stack is cloned from the manager
   $pid->ready;
   $pid;
}

=item schedule

Calls the scheduler. Please note that the current process will not be put
into the ready queue, so calling this function usually means you will
never be called again.

=cut

=item cede

"Cede" to other processes. This function puts the current process into the
ready queue and calls C<schedule>, which has the effect of giving up the
current "timeslice" to other coroutines of the same or higher priority.

=cut

=item terminate

Terminates the current process.

Future versions of this function will allow result arguments.

=cut

sub terminate {
   $current->cancel;
   &schedule;
   die; # NORETURN
}

=back

# dynamic methods

=head2 PROCESS METHODS

These are the methods you can call on process objects.

=over 4

=item new Coro \&sub [, @args...]

Create a new process and return it. When the sub returns the process
automatically terminates. To start the process you must first put it into
the ready queue by calling the ready method.

The coderef you submit MUST NOT be a closure that refers to variables
in an outer scope. This does NOT work. Pass arguments into it instead.

=cut

sub _newcoro {
   terminate &{+shift};
}

sub new {
   my $class = shift;
   bless {
      _coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
   }, $class;
}

=item $process->ready

Put the current process into the ready queue.

=cut

=item $process->cancel

Like C<terminate>, but terminates the specified process instead.

=cut

sub cancel {
   push @destroy, $_[0];
   $manager->ready;
}

=item $oldprio = $process->prio($newprio)

Sets the priority of the process. Higher priority processes get run before
lower priority processes. Priorities are smalled signed integer (currently
-4 .. +3), that you can refer to using PRIO_xxx constants (use the import
tag :prio to get then):

   PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
       3    >     1     >      0      >    -1    >    -3     >    -4

   # set priority to HIGH
   current->prio(PRIO_HIGH);

The idle coroutine ($Coro::idle) always has a lower priority than any
existing coroutine.

Changing the priority of the current process will take effect immediately,
but changing the priority of processes in the ready queue (but not
running) will only take effect after the next schedule (of that
process). This is a bug that will be fixed in some future version.

=cut

sub prio {
   my $old = $_[0]{prio};
   $_[0]{prio} = $_[1] if @_ > 1;
   $old;
}

=item $newprio = $process->nice($change)

Similar to C<prio>, but subtract the given value from the priority (i.e.
higher values mean lower priority, just as in unix).

=cut

sub nice {
   $_[0]{prio} -= $_[1];
}

=back

=cut

1;

=head1 BUGS/LIMITATIONS

 - could be faster, especially when the core would introduce special
   support for coroutines (like it does for threads).
 - there is still a memleak on coroutine termination that I could not
   identify. Could be as small as a single SV.
 - this module is not well-tested.
 - if variables or arguments "disappear" (become undef) or become
   corrupted please contact the author so he cen iron out the
   remaining bugs.
 - this module is not thread-safe. You must only ever use this module from
   the same thread (this requirement might be loosened in the future to
   allow per-thread schedulers, but Coro::State does not yet allow this).

=head1 SEE ALSO

L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,
L<Coro::Signal>, L<Coro::State>, L<Coro::Event>, L<Coro::RWLock>,
L<Coro::Handle>, L<Coro::Socket>.

=head1 AUTHOR

 Marc Lehmann <pcg@goof.com>
 http://www.goof.com/pcg/marc/

=cut

Revision:	1.31
Committed:	Sat Aug 11 23:10:56 2001 UTC (22 years, 9 months ago) by root
Branch:	MAIN
Changes since 1.30:	+44 -1 lines
Log Message:	* empty log message *
#	Content
1	=head1 NAME
2
3	Coro - coroutine process abstraction
4
5	=head1 SYNOPSIS
6
7	use Coro;
8
9	async {
10	# some asynchronous thread of execution
11	};
12
13	# alternatively create an async process like this:
14
15	sub some_func : Coro {
16	# some more async code
17	}
18
19	cede;
20
21	=head1 DESCRIPTION
22
23	This module collection manages coroutines. Coroutines are similar to
24	Threads but don't run in parallel.
25
26	This module is still experimental, see the BUGS section below.
27
28	In this module, coroutines are defined as "callchain + lexical variables
29	+ @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own
30	callchain, it's own set of lexicals and it's own set of perl's most
31	important global variables.
32
33	=cut
34
35	package Coro;
36
37	use Coro::State;
38
39	use base Exporter;
40
41	$VERSION = 0.45;
42
43	@EXPORT = qw(async cede schedule terminate current);
44	%EXPORT_TAGS = (
45	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
46	);
47	@EXPORT_OK = @{$EXPORT_TAGS{prio}};
48
49	{
50	my @async;
51	my $init;
52
53	# this way of handling attributes simply is NOT scalable ;()
54	sub import {
55	Coro->export_to_level(1, @_);
56	my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
57	*{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
58	my ($package, $ref) = (shift, shift);
59	my @attrs;
60	for (@_) {
61	if ($_ eq "Coro") {
62	push @async, $ref;
63	unless ($init++) {
64	eval q{
65	sub INIT {
66	&async(pop @async) while @async;
67	}
68	};
69	}
70	} else {
71	push @attrs, $_;
72	}
73	}
74	return $old ? $old->($package, $ref, @attrs) : @attrs;
75	};
76	}
77
78	}
79
80	=item $main
81
82	This coroutine represents the main program.
83
84	=cut
85
86	our $main = new Coro;
87
88	=item $current (or as function: current)
89
90	The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course).
91
92	=cut
93
94	# maybe some other module used Coro::Specific before...
95	if ($current) {
96	$main->{specific} = $current->{specific};
97	}
98
99	our $current = $main;
100
101	sub current() { $current }
102
103	=item $idle
104
105	The coroutine to switch to when no other coroutine is running. The default
106	implementation prints "FATAL: deadlock detected" and exits.
107
108	=cut
109
110	# should be done using priorities :(
111	our $idle = new Coro sub {
112	print STDERR "FATAL: deadlock detected\n";
113	exit(51);
114	};
115
116	# this coroutine is necessary because a coroutine
117	# cannot destroy itself.
118	my @destroy;
119	my $manager = new Coro sub {
120	while() {
121	delete ((pop @destroy)->{_coro_state}) while @destroy;
122	&schedule;
123	}
124	};
125
126	# static methods. not really.
127
128	=head2 STATIC METHODS
129
130	Static methods are actually functions that operate on the current process only.
131
132	=over 4
133
134	=item async { ... } [@args...]
135
136	Create a new asynchronous process and return it's process object
137	(usually unused). When the sub returns the new process is automatically
138	terminated.
139
140	# create a new coroutine that just prints its arguments
141	async {
142	print "@_\n";
143	} 1,2,3,4;
144
145	The coderef you submit MUST NOT be a closure that refers to variables
146	in an outer scope. This does NOT work. Pass arguments into it instead.
147
148	=cut
149
150	sub async(&@) {
151	my $pid = new Coro @_;
152	$manager->ready; # this ensures that the stack is cloned from the manager
153	$pid->ready;
154	$pid;
155	}
156
157	=item schedule
158
159	Calls the scheduler. Please note that the current process will not be put
160	into the ready queue, so calling this function usually means you will
161	never be called again.
162
163	=cut
164
165	=item cede
166
167	"Cede" to other processes. This function puts the current process into the
168	ready queue and calls C<schedule>, which has the effect of giving up the
169	current "timeslice" to other coroutines of the same or higher priority.
170
171	=cut
172
173	=item terminate
174
175	Terminates the current process.
176
177	Future versions of this function will allow result arguments.
178
179	=cut
180
181	sub terminate {
182	$current->cancel;
183	&schedule;
184	die; # NORETURN
185	}
186
187	=back
188
189	# dynamic methods
190
191	=head2 PROCESS METHODS
192
193	These are the methods you can call on process objects.
194
195	=over 4
196
197	=item new Coro \&sub [, @args...]
198
199	Create a new process and return it. When the sub returns the process
200	automatically terminates. To start the process you must first put it into
201	the ready queue by calling the ready method.
202
203	The coderef you submit MUST NOT be a closure that refers to variables
204	in an outer scope. This does NOT work. Pass arguments into it instead.
205
206	=cut
207
208	sub _newcoro {
209	terminate &{+shift};
210	}
211
212	sub new {
213	my $class = shift;
214	bless {
215	_coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
216	}, $class;
217	}
218
219	=item $process->ready
220
221	Put the current process into the ready queue.
222
223	=cut
224
225	=item $process->cancel
226
227	Like C<terminate>, but terminates the specified process instead.
228
229	=cut
230
231	sub cancel {
232	push @destroy, $_[0];
233	$manager->ready;
234	}
235
236	=item $oldprio = $process->prio($newprio)
237
238	Sets the priority of the process. Higher priority processes get run before
239	lower priority processes. Priorities are smalled signed integer (currently
240	-4 .. +3), that you can refer to using PRIO_xxx constants (use the import
241	tag :prio to get then):
242
243	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
244	3 > 1 > 0 > -1 > -3 > -4
245
246	# set priority to HIGH
247	current->prio(PRIO_HIGH);
248
249	The idle coroutine ($Coro::idle) always has a lower priority than any
250	existing coroutine.
251
252	Changing the priority of the current process will take effect immediately,
253	but changing the priority of processes in the ready queue (but not
254	running) will only take effect after the next schedule (of that
255	process). This is a bug that will be fixed in some future version.
256
257	=cut
258
259	sub prio {
260	my $old = $_[0]{prio};
261	$_[0]{prio} = $_[1] if @_ > 1;
262	$old;
263	}
264
265	=item $newprio = $process->nice($change)
266
267	Similar to C<prio>, but subtract the given value from the priority (i.e.
268	higher values mean lower priority, just as in unix).
269
270	=cut
271
272	sub nice {
273	$_[0]{prio} -= $_[1];
274	}
275
276	=back
277
278	=cut
279
280	1;
281
282	=head1 BUGS/LIMITATIONS
283
284	- could be faster, especially when the core would introduce special
285	support for coroutines (like it does for threads).
286	- there is still a memleak on coroutine termination that I could not
287	identify. Could be as small as a single SV.
288	- this module is not well-tested.
289	- if variables or arguments "disappear" (become undef) or become
290	corrupted please contact the author so he cen iron out the
291	remaining bugs.
292	- this module is not thread-safe. You must only ever use this module from
293	the same thread (this requirement might be loosened in the future to
294	allow per-thread schedulers, but Coro::State does not yet allow this).
295
296	=head1 SEE ALSO
297
298	L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,
299	L<Coro::Signal>, L<Coro::State>, L<Coro::Event>, L<Coro::RWLock>,
300	L<Coro::Handle>, L<Coro::Socket>.
301
302	=head1 AUTHOR
303
304	Marc Lehmann <pcg@goof.com>
305	http://www.goof.com/pcg/marc/
306
307	=cut
308